Diesel engine low-idle-speed circulation fuel injection quantity determining method, control system and diesel engine thereof

Abstract

The invention discloses a diesel engine low-idle-speed circulation fuel injection quantity determining method, a control system and a diesel engine thereof, and belongs to the technical field of diesel engine control. The characteristic parameters of the instantaneous rotating speed of the diesel engine are learned, the learned characteristic parameters are used for predicting the low-idle-speed circulating fuel injection quantity needed by low-idle-speed control of the engine, and intelligent low-idle-speed control of the engine is achieved. In the low-idle-speed operation process, the self-learning control method continuously conducts self-correction learning on the characteristic parameters, the characteristic parameters are continuously updated, the low-idle-speed control effect of the engine is optimized, and the stability and robustness of low-idle-speed control of the engine are improved. According to the method, engine low-idle-speed control is completed based on self-learning, good adaptability and applicability are achieved, complex control parameter calibration is not needed, implementation and application in an embedded system are facilitated, and popularization is facilitated.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of diesel engine control technology, and in particular to a method for determining the fuel injection amount in a low idle cycle of a diesel engine, a control system, and a diesel engine thereof. Background Art

[0002] Low idle speed is the lowest speed at which the engine can run stably under no-load conditions. After the engine is successfully started, it will enter the low idle speed condition and wait for the driver's subsequent operation. Under the low idle speed condition, the engine only needs to overcome the friction resistance of its internal parts and maintain its own operation without outputting power to the outside. The control of low idle speed is crucial to the engine performance. Too high or too low low idle speed may have adverse effects on the engine. By optimizing the control of low idle speed, the fuel economy of the engine can be improved, the engine life can be extended, the driving comfort of the vehicle can be improved, and the emission of pollutants can be reduced.

[0003] The low idle speed control of diesel engines is usually based on process feedback control theory, and PID is used to adjust the circulating injection amount of the diesel engine in a closed loop according to the low idle speed target speed and the actual speed to achieve the low idle speed control of the engine. In addition, the PID parameters need to be finely and complexly coupled and calibrated to achieve a good low idle speed control effect. In order to improve the stability of the low idle speed of the engine, the current technical solutions are based on the PID classic control architecture, and the PID control parameters or PID output are compensated according to many conditions such as speed deviation information, environmental information, vehicle information, etc., thereby improving the low idle speed control effect to a certain extent.

[0004] Although the PID-based low idle control technology is very mature, the PID parameters need to be calibrated separately for different engine models. The product development cycle is long and the cost is high. The calibration quality of the parameters varies depending on the technical level of the calibration engineer. In addition, due to manufacturing and processing deviations, the calibrated PID parameters have poor adaptability and cannot ensure that each engine of the same model achieves the best effect. However, PID parameter calibration is time-consuming and labor-intensive, and it is impossible to calibrate each engine individually. Therefore, there is an urgent need for a method that can perform low idle intelligent control based on the characteristic parameters of the engine itself to replace the traditional control method. Without calibration, the low idle control of each engine can be optimized through self-learning, thereby improving the robustness and stability of low idle control. Summary of the invention

[0005] In order to overcome the above technical defects and achieve the purpose of improving the robustness and stability of low idle control, the present application provides a method for determining the injection amount of a diesel engine in a low idle cycle, and its technical solution is as follows:

[0006] S1. After the engine is started, when the value of the initial parameter learning flag variable is 0, the cyclic injection amount is automatically set through the automated test to accelerate and decelerate the engine. The learning is centered on the low idle target speed. The initial parameter learning requires the instantaneous speed characteristic parameters within the speed threshold range. When the stop condition is reached, the initial parameter learning of the instantaneous speed characteristic is stopped and the initial parameter learning flag variable is set to 1.

[0007] The instantaneous speed characteristic parameters of the engine include the speed n sart , speed n max , speed n end , acceleration time t a , deceleration time t d , acceleration a a and deceleration a d ;

[0008] S2. During the initial parameter learning process of the instantaneous speed characteristics, an acceleration-injection amount mapping table is generated. The acceleration-injection amount mapping table is the correspondence between acceleration and cyclic injection amount within the speed threshold range required for the initial parameter learning, and is used to determine the cyclic injection amount of low idle control.

[0009] Optionally, in some possible implementations of the present application, in S1, the method for determining the instantaneous speed characteristic parameter of the engine specifically includes:

[0010] S1.1. Determine the speed n by detecting the turning point of the instantaneous engine speed sart , speed n max , speed n end , acceleration time t a , deceleration time t d , speed n sart and n end The corresponding speed inflection point is a positive inflection point, and the speed n max The corresponding inflection point is a negative inflection point;

[0011] S1.2, according to the speed n sart , speed n max , speed n end , acceleration time t a , deceleration time t d Calculate the acceleration a a and deceleration a d , which is calculated as follows:

[0012] .

[0013] Optionally, in some possible implementations of the present application, the speed threshold range required for initial parameter learning is a speed range , where the speed is a speed threshold value less than the low idle target speed, the speed is a speed threshold value greater than the low idle target speed;

[0014] The setting method of the cycle injection amount is: , where is the cyclic injection amount of the initial parameter learning process, is the maximum injection amount, For the test order, , is the number of trials when the stopping condition is reached, is the change gradient of the injection amount;

[0015] In the initial parameter learning process, The injection amount of each test cycle The corresponding characteristic parameter calculation method is:

[0016] , , , ;

[0017] The stopping condition during the initial parameter learning process is the cycle injection amount The acceleration of the engine Less than or equal to 0 or cycle injection amount q i Failure to increase the engine speed to the specified time threshold ;

[0018] After the initial parameter learning stops, when the stop condition is reached The value of is the number of trials for initial parameter learning , respectively, to obtain the previous The average of the acceleration time, deceleration time and deceleration of the test is taken as the final acceleration time. , deceleration time And deceleration , and its calculation formula is as follows:

[0019] , , .

[0020] Optionally, in some possible implementations of the present application, the method further includes:

[0021] When the value of the initial parameter learning flag variable is 1, the following low idle speed control is performed:

[0022] S3, based on the engine speed The control target is equal to the low idle target speed, the acceleration required for low idle control is predicted by the instantaneous speed characteristic parameters, and the required low idle cycle injection amount is determined by the generated acceleration-injection amount mapping table, thereby controlling the engine to operate stably in low idle conditions.

[0023] Optionally, in some possible implementations of the present application, the calculation of the low idle cycle injection amount specifically includes:

[0024] S3.1. Predict the end speed of the current instantaneous speed cycle ,

[0025] ;

[0026] S3.2. Predict the maximum speed of the next instantaneous speed cycle ,

[0027] ;

[0028] S3.3, according to the end speed of the current instantaneous speed cycle and the maximum speed of the next instantaneous speed cycle Calculate the required speed increase and then calculate the required acceleration. The calculation formula is:

[0029] ;

[0030] S3.4. According to the acceleration, the required low idle cycle injection amount q is determined by interpolation of the mapping table. The calculation formula is: .

[0031] Optionally, in some possible implementations of the present application, the method further includes:

[0032] S4. During the low idle speed control process, based on the method for determining the characteristic parameters of the instantaneous speed, each characteristic parameter of the instantaneous speed is learned and corrected, and the deceleration, deceleration duration, acceleration duration, and acceleration-injection amount mapping table are updated;

[0033] The self-correction method of instantaneous speed characteristic parameters is: , , ;

[0034] The calculation formula for fuel injection quantity adjustment is:

[0035] , .

[0036] A control system is also provided in an embodiment of the present application for executing the method for determining the fuel injection amount in a low idle cycle of a diesel engine as described in any of the above items.

[0037] A diesel engine is also provided in an embodiment of the present application, which is controlled by the control system as described above, and executes the method for determining the low idle cycle injection amount of the diesel engine as described in any of the above items under the control of the control system, so that the diesel engine operates under a low idle control condition.

[0038] The embodiments of the present application adopt the above technical solution to achieve the following technical effects:

[0039] 1. The initial parameter learning of the instantaneous speed characteristic of the present application is carried out automatically without human intervention, and the control parameters unique to each engine can be obtained to realize the intelligent control of the low idle speed of the diesel engine.

[0040] 2. The low idle control method of the present application does not require complicated control parameter calibration, is not dependent on the engine structure and number of cylinders, and can adapt to engine manufacturing deviations, usage wear, aging errors, etc., and has good adaptability and applicability.

[0041] 3. The low idle control method of the present application continuously performs self-correction learning on the characteristic parameters. As the learning process progresses, the control accuracy becomes higher and higher, and the stability and robustness of the control method become better, so that the control process of the engine low idle speed is continuously optimized.

[0042] 4. The low idle speed control method of the present application is easy to implement and apply in embedded systems, and is conducive to promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings exemplarily illustrate the embodiments and constitute a part of the specification, and together with the text description of the specification, are used to explain the exemplary implementation of the embodiments. The embodiments shown are for illustrative purposes only and do not limit the scope of the claims. In all drawings, the same reference numerals refer to similar but not necessarily identical elements.

[0044] Figure 1 A schematic flow chart of a method for determining the fuel injection quantity in a low idle cycle of a diesel engine in this application;

[0045] Figure 2 It is a schematic diagram of characteristic parameters of instantaneous engine speed;

[0046] Figure 3 Schematic diagram of the initial parameter self-learning process;

[0047] Figure 4 It is a schematic diagram of the engine speed acceleration-injection amount mapping;

[0048] Figure 5 This is a schematic diagram of the engine low idle control logic;

[0049] Figure 6 This is the logic diagram of fuel injection quantity control during the initial parameter learning process;

[0050] Figure 7 A schematic diagram of a process flow of low idle speed control in this application;

[0051] Figure 8 This is a schematic diagram for calculating the increase in speed;

[0052] Fig. 9 This is a schematic diagram of the acceleration-injection amount mapping table self-correction. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0054] It should be noted that the descriptions involving "first", "second", etc. in the embodiments of the present application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0055] In the description of the present application, it should be understood that the numerical labels before the steps do not indicate the order in which the steps are executed, but are only used to facilitate the description of the present application and to distinguish each step, and therefore should not be understood as a limitation on the present application.

[0056] In order to improve the robustness and stability of low idle speed control, a method for determining the low idle speed cycle injection amount of a diesel engine is provided in an embodiment of the present application, which realizes that during the low idle speed control process, the characteristic parameter self-correction learning is continuously performed by self-learning, and the low idle speed cycle injection amount of the engine is predicted to achieve low idle speed control of the engine. Since the prediction is real-time, its prediction accuracy is high, and the stability and robustness of the low idle speed control can be improved. The technical solution is as follows:

[0057] Embodiment 1

[0058] See also Figure 1 In the embodiment of the present application, the method for determining the fuel injection amount of a diesel engine in a low idle cycle includes:

[0059] S1. After the engine is started, when the value of the initial parameter learning flag variable is 0, the cyclic injection amount is automatically set through the automated test to accelerate and decelerate the engine. The learning is centered on the low idle target speed. The initial parameter learning requires the instantaneous speed characteristic parameters within the speed threshold range until the stop condition is reached. The initial parameter learning of the instantaneous speed characteristic is stopped and the initial parameter learning flag variable is set to 1.

[0060] Low idle speed is generally a fixed target, such as 800 rpm. From the perspective of control, the more precise the better, so the low idle speed condition is around 800, close to 800. The engine operating around 800 rpm is a low idle speed condition. The speed range for initial parameter learning is a speed range centered on the low idle target speed of 800, such as 600~1000. In this speed range, the average value is obtained through initial parameter learning as a characteristic parameter for controlling low idle speed (800). Therefore, the speed threshold range described in this application is used for initial parameter learning, not for low idle speed control.

[0061] Specifically, after the engine is started, the initial parameter learning flag variable is detected to determine whether its value is 0. If it is 0, the initial parameter learning of the instantaneous speed characteristic is started, and if it is 1, low idle speed control is directly performed. The specific control method is shown in the second embodiment below. The initial parameter learning flag variable can be read from the EEPROM in the engine ECU.

[0062] Specifically, the instantaneous speed characteristic parameters of the engine include the speed , speed , speed , acceleration time , deceleration time , acceleration and deceleration , such as Figure 2 shown. It is the speed value when the engine starts to accelerate when the power generated by the combustion of the engine fuel is greater than the power consumption; It is the speed value when the engine starts to decelerate when the power generated by the engine fuel is less than the power consumption. It is also the maximum speed value in an instantaneous speed cycle. It is the speed at which the engine decelerates to the point where the power generated by the combustion of the subsequent cylinders is greater than the engine resistance again. It is the end speed of an instantaneous speed cycle. , which is also the subsequent instantaneous speed cycle ; The engine speed is Speed ​​up to The time spent, is the acceleration of the acceleration process; The engine speed is Slow down to The time spent, is the deceleration rate of the deceleration process.

[0063] Optionally, the method for determining the instantaneous speed characteristic parameter of the engine specifically includes the following S1.1 and S1.2:

[0064] S1.1. Determine the speed n by detecting the turning point of the instantaneous engine speed sart , speed , speed , acceleration time , deceleration time , speed and The corresponding speed inflection point is the positive inflection point, and the speed The corresponding inflection point is a negative inflection point.

[0065] The method for determining the instantaneous speed characteristic parameters by inflection point detection is as follows: in each running step, the change amount of the engine speed is calculated and judged as follows: when the engine speed change amount changes from a negative value to a value greater than or equal to 0, a positive inflection point is detected, and the speed value corresponding to the positive inflection point is , which is also the next speed cycle When a positive inflection point is detected, the timer is initialized and starts to count t a When the engine speed changes from a positive value to a value less than or equal to 0, a negative inflection point is detected. The speed value corresponding to the negative inflection point is When a negative inflection point is detected, the timer value is assigned to , and then initialize the timer and start When the positive inflection point is detected again, the timer value is assigned to , and then initialize the timer and start counting t again a Timing is performed to form a closed loop of the method for determining the instantaneous speed characteristic parameters.

[0066] The above-mentioned operation step refers to the time interval for the instantaneous speed characteristic parameter determination method to run in the control system, which is 1ms.

[0067] S1.2, according to the speed , speed , speed , acceleration time , deceleration time Calculating acceleration and deceleration , which is calculated as follows:

[0068] .

[0069] Specifically, the speed threshold range required for initial parameter learning is the speed range , where the speed is a speed threshold value less than the low idle target speed, the speed is a speed threshold greater than the low idle target speed. When the engine speed is greater than the speed threshold, the cycle injection amount is set to accelerate the engine. When the fuel injection volume is set to 0, the fuel injection is stopped to slow down the engine. This cycle is repeated until the initial parameter self-learning stop condition is reached. The initial parameter self-learning process is as follows: Figure 3 shown.

[0070] Specifically, the setting method of the cycle injection amount is as follows: , where is the cyclic injection amount of the initial parameter learning process, is the maximum injection amount, For the test order, , is the number of trials when the stopping condition is reached, is the change gradient of the injection amount.

[0071] Specific options, such as Figure 3 As shown in the figure, during the initial parameter learning process, The injection amount of each test cycle The corresponding characteristic parameter calculation method is:

[0072] , , , ,

[0073] In the formula, is the injection amount of the i-th test in the initial parameter learning process The corresponding average acceleration time is is the fuel injection amount for the ith test The corresponding average deceleration time is is the injection amount q of the i-th test i The corresponding average acceleration is is the injection amount q of the i-th test i The corresponding average deceleration value, j is the order of the complete speed cycle that occurs during the acceleration process of the engine in the i-th test, , For the The number of complete speed cycles that occur during the acceleration of the test engine.

[0074] Specifically, the stopping condition in the initial parameter learning process is the cycle injection amount q i The acceleration of the engine Less than or equal to 0 or cycle injection amount q i Failure to get the engine speed to n within the specified time threshold Hi When the stop condition is reached, the automated test is stopped. At this time, the value of i is the value of the number of trials N for initial parameter learning. The average values ​​of the acceleration time, deceleration time, and deceleration of the first (N-1) trials are taken as the final acceleration time t a , deceleration time t d and deceleration a d , and its calculation formula is as follows:

[0075] , , .

[0076] It should be noted that there is no need to ask The average value is a a , And the corresponding q i A key-value pair is formed and stored in the acceleration-injection quantity mapping table for determining the cycle injection quantity according to the acceleration required for low idle speed control. With q i The mapping expression is as follows Figure 4 As shown, is the key, q i The specified time threshold is 30 seconds.

[0077] S2. During the initial parameter learning process, an acceleration-injection amount mapping table is generated. The acceleration-injection amount mapping table is a correspondence between acceleration and cyclic injection amount at corresponding speeds within a speed threshold range required for initial parameter learning, and is used to determine the cyclic injection amount of low idle control.

[0078] Based on the characteristic parameters determined in the above diesel engine low idle cycle injection quantity determination method and the generated acceleration-injection quantity mapping table, the control logic of the diesel engine low idle control method is as follows: Figure 5As shown. After the ECU is powered on, the characteristic parameters and initial parameter learning flag variables are first read from the EEPROM in the ECU. If the value of the initial learning flag variable is 0, it means that the initial characteristic parameter learning has not been performed yet, and an initial characteristic parameter learning is required. If the value of the initial learning flag variable is 1, it means that the initial characteristic parameter learning has been performed, and the low idle control is directly entered. In the low idle control link, the cyclic injection amount used to control the engine is predicted according to the characteristic parameters of the instantaneous speed, so as to control the engine to operate in a low idle condition. In the low idle control process, the instantaneous speed of the engine in the low idle condition is learned and the characteristic parameters are self-corrected to improve the stability of the engine low idle control. When the engine is stopped, the corrected characteristic parameters are stored in the EEPROM so that the low idle speed can be better controlled the next time the engine runs.

[0079] Before the initial parameter learning is performed, the default values ​​of all characteristic parameters are 0. The characteristic parameters cannot be used to control the fuel volume of the engine at low idle speed. Therefore, the initial parameter learning must be performed first. The initial parameter learning is performed through automated testing. The control logic of the learning process is as follows: Figure 6 After the engine starts successfully, it immediately enters the initial parameter learning state. By automatically setting the cycle injection amount, the automatic test is performed to accelerate and decelerate the engine, thereby learning the speed n Lo ~n Hi The instantaneous speed characteristic parameter within the range, where n Lo is a speed threshold value less than the low idle target speed, n Hi is a speed threshold greater than the low idle target speed. Lo and n Hi Usually, the low idle target speed is set symmetrically. For example, if the low idle speed is 800rpm, then n Lo Set to 600rpm, n Hi Set to 1000rpm. When the engine speed is lower than the speed threshold of 600rpm, set the cycle injection amount to accelerate the engine. When the engine speed is greater than the speed threshold of 1000rpm, set the cycle injection amount to 0, stop injection, and slow down the engine. Repeat this cycle until the initial parameter self-learning stop condition is reached. When setting the cycle injection amount for the first time, use the maximum injection amount q max , and each subsequent time the cycle injection amount is set, the injection amount is reduced by Δq. max and Δq can be preset in the ECU in advance according to the external characteristic oil volume of the controlled engine and the expected number of tests. The smaller Δq is, the more tests are performed by the initial parameter self-learning. The larger Δq is, the fewer tests are performed by the initial parameter self-learning. However, too few tests may result in the inability to obtain the cycle injection amount and engine acceleration a aThe relationship between Δq and Δq is usually 5 mg / cyc.

[0080] In this application, the initial parameter learning of the instantaneous speed characteristics is carried out automatically without human intervention, and the control parameters unique to each engine can be obtained to realize the intelligent control of the low idle speed of the diesel engine. In addition, the determination of the cyclic injection amount of the low idle speed control and the idle speed control can be directly obtained from the acceleration-injection amount mapping table, without the need for complicated control parameter calibration, and it is not dependent on the engine structure and the number of cylinders, and it can adapt to the engine manufacturing deviation, use wear, aging error, etc., and has good adaptability and applicability.

[0081] Embodiment 2

[0082] See also Figure 7 , if the value of the initial parameter learning flag variable is 1, the scheme for executing low idle speed control is as follows:

[0083] S3, with engine speed n end The control target is equal to the low idle target speed, the acceleration required for low idle control is predicted by the instantaneous speed characteristic parameters, and the low idle cycle injection amount is determined by the generated acceleration-injection amount mapping table, thereby controlling the engine to operate stably in a low idle condition.

[0084] After the initial parameter learning, each characteristic parameter is assigned a value. The speed increase required for idle speed control can be calculated based on the value of the characteristic parameter, thereby determining the required cycle injection amount. The calculation of the speed increase is shown in the figure below: Figure 8 As shown in (a) and (b). Since the positive inflection point of the instantaneous speed only appears after the engine burns, the calculation of the cycle injection amount must be calculated before the positive inflection point appears. In order to facilitate the calculation, the negative inflection point of the instantaneous speed is selected as the calculation time of the cycle injection amount. When it is detected that the instantaneous speed of the engine reaches the negative inflection point, according to the current maximum speed Predicted time elapsed End speed Since the purpose of idle speed control is to stabilize the engine speed at a low idle target speed, the instantaneous engine speed is It just falls on the low idle target speed as the target of the self-learning idle control method, that is, Equal to low idle target speed n Idle .according to , as well as Predictions to make Equal to n Idle Maximum speed , then according to and Calculating the low idle cycle injection quantity includes the following steps:

[0085] S3.1. Predict the end speed of the current instantaneous speed cycle .

[0086] , where is the maximum speed of the current instantaneous speed cycle, is the predicted ending speed of the current instantaneous speed cycle.

[0087] S3.2. Predict the maximum speed of the next instantaneous speed cycle .

[0088] , where n Idle is the low idle target speed, is the end speed of the next speed cycle, is the maximum speed of the next speed cycle.

[0089] S3.3, according to the end speed of the current instantaneous speed cycle and the maximum speed of the next instantaneous speed cycle Calculate the required speed increase and thus the required acceleration.

[0090] The calculation formula is: , where is the speed increment required for low idle control and is the acceleration required for the current low idle control.

[0091] When predicted Greater than expected When the engine is not needed to accelerate, Should be 0, no injection. Greater than expected When the time is greater than When the current engine speed is used as the new , recalculate according to the above calculation method ,like Figure 8 As shown in part (b).

[0092] S3.4. According to the acceleration, the required low idle cycle fuel injection amount q is determined by interpolation of the mapping table.

[0093] The calculation formula is: , where The largest value in the mapping table that is less than or equal to The acceleration value, In the mapping table The corresponding injection amount, The smallest value in the mapping table that is greater than or equal to The acceleration value, In the mapping table The corresponding injection amount, q is the low idle cycle injection amount.

[0094] S4. During the low idle speed control process, based on the method for determining the instantaneous speed characteristic parameter, each characteristic parameter of the instantaneous speed is learned and corrected, and updated to the acceleration-injection amount mapping table of the existing characteristic parameters.

[0095] Since the characteristic parameter of the initial parameter learning is the speed n Lo ~n Hi The average value of the interval is still different from the characteristic parameters of the engine running at low idle speed. Therefore, in the process of idle speed control, it is necessary to continuously learn the characteristic parameters and update the characteristic parameters in real time at a certain ratio to improve the accuracy and stability of engine low idle speed control. In the process of idle speed control, based on the characteristic parameter determination method, the characteristic parameters of each instantaneous speed are learned, and the deceleration, deceleration time, acceleration time and acceleration-injection amount mapping table are updated.

[0096] The self-correction method of instantaneous speed characteristic parameters is:

[0097] ,

[0098] ,

[0099] ,

[0100] In the formula, It is the acceleration time of a certain speed cycle during the low idle speed control process. is the deceleration time corresponding to the speed cycle, is the deceleration corresponding to the speed cycle, , and They are respectively the corrected acceleration time, deceleration time and deceleration rate.

[0101] According to Recalculate and use the injection amount corresponding to the speed cycle Adjust the fuel quantities corresponding to adjacent accelerations in the acceleration-fuel injection quantity mapping table. The fuel quantity adjustment diagram is as follows: Fig. 9 As shown. Corresponding fuel injection amount Less than When the injection amount q is obtained by interpolation of the mapping table, the injection amount corresponding to the adjacent acceleration in the mapping table needs to be reduced, otherwise the injection amount needs to be increased.

[0102] The calculation formula for fuel injection quantity adjustment is:

[0103] , ,

[0104] In the formula, Based on The recalculated acceleration corresponding to the speed cycle, is the fuel injection amount corresponding to the speed cycle. The largest value in the mapping table that is less than or equal to The acceleration value, In the mapping table The corresponding injection amount, The smallest value in the mapping table that is greater than or equal to The acceleration value, In the mapping table The corresponding injection amount, q, is The injection amount obtained by interpolation of the acceleration-injection amount mapping table, After correction The corresponding injection amount, After correction The corresponding fuel injection amount.

[0105] When the engine is stopped, the self-corrected characteristic parameters and acceleration-injection amount mapping table will be stored in the EEPROM of the ECU so that the latest characteristic parameters can be used to control the low idle speed of the engine when it is restarted. After the initial characteristic parameter learning, the value of the initial learning flag variable has been set to 1. When the engine is started again, it is not necessary to learn the initial characteristic parameters again, and low idle speed control is performed directly according to the learned characteristic parameters. However, during the low idle speed control process, characteristic parameter self-correction learning will still be performed to continuously optimize the characteristic parameters of low idle speed control and improve the effect of engine low idle speed control.

[0106] The low idle control in the present application can continuously perform self-correction learning on the characteristic parameters. As the learning process deepens, the control accuracy becomes higher and higher, and the stability and robustness of the control method become better, so that the control process of the engine low idle speed is continuously optimized. At the same time, it is also easy to implement and apply in embedded systems, which is conducive to promotion.

[0107] Obviously, those skilled in the art should understand that the modules or steps of the above-mentioned embodiments of the present application can be implemented by general-purpose computer devices, they can be concentrated on a single computer device, or distributed on a network composed of multiple computer devices, optionally, they can be implemented by executable program codes of computer devices, so that they can be stored in a storage device and executed by the computer device, and in some cases, the steps shown or described can be executed in a different order from that herein, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. In this way, the embodiments of the present application are not limited to any specific combination of hardware and software.

[0108] It should be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for determining the fuel injection amount of a diesel engine at low idle speed cycle, characterized in that: include: S1. After the engine is started, when the value of the initial parameter learning flag variable is 0, the cyclic injection amount is automatically set through the automated test to accelerate and decelerate the engine. The learning is centered on the low idle target speed. The initial parameter learning requires the instantaneous speed characteristic parameters within the speed threshold range. When the stop condition is reached, the initial parameter learning of the instantaneous speed characteristic is stopped and the initial parameter learning flag variable is set to 1. The instantaneous speed characteristic parameters of the engine include the speed , speed , speed , acceleration time , deceleration time , acceleration and deceleration ; S2. During the initial parameter learning process of the instantaneous speed characteristics, an acceleration-injection amount mapping table is generated. The acceleration-injection amount mapping table is the correspondence between acceleration and cyclic injection amount within the speed threshold range required for the initial parameter learning, and is used to determine the cyclic injection amount of low idle control.

2. The method according to claim 1, characterized in that In S1, the method for determining the instantaneous speed characteristic parameter of the engine specifically includes: S1.

1. Determine the speed by detecting the turning point of the instantaneous engine speed , speed , speed , acceleration time , deceleration time , speed and The corresponding speed inflection point is the positive inflection point, and the speed The corresponding inflection point is a negative inflection point; S1.2, according to the speed , speed , speed , acceleration time , deceleration time Calculating acceleration and deceleration , which is calculated as follows: 。 3. The method according to claim 1 or 2, characterized in that: The speed threshold range required for initial parameter learning is the speed range , where the speed is a speed threshold value less than the low idle target speed, speed n Hi is a speed threshold value greater than the low idle target speed; The setting method of the cycle injection amount is: , where q is the cyclic injection amount in the initial parameter learning process, is the maximum injection amount, i is the test order, , is the number of trials when the stopping condition is reached, is the change gradient of the injection amount; In the initial parameter learning process, The injection amount of each test cycle The corresponding characteristic parameter calculation method is: ； The stopping condition in the initial parameter learning process is the cycle injection quantity q i The acceleration of the engine Less than or equal to 0 or cycle injection amount q i Failure to get the engine speed to n within the specified time threshold Hi ; After the initial parameter learning stops, the value of i when the stopping condition is reached is the value of the number of trials N of the initial parameter learning. The average value of the acceleration time, deceleration time and deceleration of the previous (N-1) trials is taken as the final acceleration time t a , deceleration time t d and deceleration a d , and its calculation formula is as follows: 。 4. The method according to claim 1, characterized in that The method further comprises: When the value of the initial parameter learning flag variable is 1, the following low idle speed control is performed: S3, with engine speed n end The control target is equal to the low idle target speed, the acceleration required for low idle control is predicted by the instantaneous speed characteristic parameters, and the low idle cycle injection amount is determined by the generated acceleration-injection amount mapping table, thereby controlling the engine to operate stably in a low idle condition.

5. The method according to claim 4, characterized in that The calculation of low idle cycle injection quantity specifically includes: S3.

1. Predict the end speed of the current instantaneous speed cycle , ； S3.

2. Predict the maximum speed of the next instantaneous speed cycle , ； S3.3, according to the end speed of the current instantaneous speed cycle and the maximum speed of the next instantaneous speed cycle Calculate the required speed increase and then calculate the required acceleration. The calculation formula is: ； S3.

4. According to the acceleration, the required low idle cycle injection amount q is determined by interpolation of the mapping table. The calculation formula is: .

6. The method according to claim 4 or 5, characterized in that: The method further comprises: S4. During the low idle speed control process, based on the method for determining the characteristic parameters of the instantaneous speed, each characteristic parameter of the instantaneous speed is learned and corrected, and the deceleration, deceleration duration, acceleration duration, and acceleration-injection amount mapping table are updated; The self-correction method of instantaneous speed characteristic parameters is: ， ， ； The calculation formula for fuel injection quantity adjustment is: 。 7. A control system for executing the method for determining the fuel injection quantity in a low idle cycle of a diesel engine as described in any one of claims 1 to 6.

8. A diesel engine, which is controlled by the control system as claimed in claim 7, and the method for determining the low idle cycle injection quantity of the diesel engine as claimed in any one of claims 1 to 6 is executed under the control of the control system, so that the diesel engine operates under a low idle control condition.

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